linux-kernel - Re: [patch 1/5] tracehook: Provide TIF_NOTIFY

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 1 Aug 2019 17:10:35 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Ingo Molnar <mingo@...nel.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Julia Cartwright <julia@...com>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, kvm@...r.kernel.org,
        Radim Krcmar <rkrcmar@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        John Stultz <john.stultz@...aro.org>,
        Andy Lutomirski <luto@...nel.org>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>
Subject: Re: [patch 1/5] tracehook: Provide TIF_NOTIFY_RESUME handling for
 KVM

On Thu, 1 Aug 2019, Peter Zijlstra wrote:
> On Thu, Aug 01, 2019 at 04:32:51PM +0200, Thomas Gleixner wrote:
> > +#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
> > +/**
> > + * tracehook_handle_notify_resume - Notify resume handling for virt
> > + *
> > + * Called with interrupts and preemption enabled from VMENTER/EXIT.
> > + */
> > +void tracehook_handle_notify_resume(void)
> > +{
> > +	local_irq_disable();
> > +	while (test_and_clear_thread_flag(TIF_NOTIFY_RESUME)) {
> > +		local_irq_enable();
> > +		tracehook_notify_resume(NULL);
> > +		local_irq_disable();
> > +	}
> > +	local_irq_enable();
> 
> I'm confused by the IRQ state swizzling here, what is it doing?

Hmm, right. It's not really needed. Modeled it after the user space return
code, but the KVM case is different because it evaluates the TIF bit again
before entering the VM with interrupts disabled anyway.

I'll remove the brainfart in V2.

Thanks,

	tglx